Surface characteristic analysis apparatus

ABSTRACT

In order to establish processing techniques capable of making multi-tip probes with sub-micron intervals and provide such microscopic multi-tip probes, there is provided an outermost surface analysis apparatus for semiconductor devices etc. provided with a function for enabling positioning to be performed in such a manner that there is no influence on measurement in electrical measurements at an extremely small region using this microscopic multi-tip probe, and there are provided the steps of making a cantilever  1  formed with a plurality of electrodes  3  using lithographic techniques, and forming microscopic electrodes  6  minute in pitch by sputtering or gas-assisted etching a distal end of the cantilever  1  using a focused charged particle beam or using CVD.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a division of U.S. application Ser. No.10/651,526, filed on Aug. 29, 2003 and now U.S. Pat. No. 6,953,519,which is hereby incorporated by reference, and priority thereto forcommon subject matter is hereby claimed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a scanning probe microscope accordingto the four-tip probe method which the microscope is to be used in, forexample, semiconductor process evaluation, and also to a probe suitablefor analyzing an ultra-surface region of a sample when used in thescanning probe microscope.

2. Description of Related Art

The invention of the transistor evolved from studies of the electricalcharacteristics of a semiconductor surface, particularly the surfaceelectron state. However, with respect to electrical conduction due tothe state of surface electrons themselves, many points have been leftunanalyzed until today. This “surface state conduction” is extremelydifficult to measure because electricity runs only in one or twoelectron layers of a crystal surface. However, thanks to the developmentof new measuring and inspecting techniques, such as a four-tip probescanning tunnel microscope operating in an ultra-high vacuum and amicroscopic four-tip probe, direct measurement of the surface stateconduction has become possible and very interesting conductioncharacteristics have become revealed as a result. To this end, it hasbeen determined that the electron state of a semiconductor surface has aunique characteristic totally different from that of the bulk state. Inthe electron device field, apparatuses of this type will play animportant role in research and development of electron devices.

In an evaluating apparatus using a scanning tunnel microscope accordingto the four-tip probe method, four probe tips are arranged linearly atregular distances, a current is caused to flow into a sample from theouter two of the probe tips, and a voltage drop caused due to theelectrical resistance of the sample is measured by the inner two of theprobe tips. At such time, because there is only a very slight currentflowing in these probe tips, only a voltage drop V on the sample can bemeasured without influence of the contact resistance at a point ofcontact of the probe tips with the sample. An electrical resistanceaccording to the four-tip probe method is obtained by R=V/I where I is ameasured current. As shown in FIGS. 10A and 10B there is a correlationbetween the inter-probe-tip distance and the depth of probing into asample. In order to obtain information of the ultra-surface of thesample, it is essential to arrange the probes at the correspondingnarrow distances shown in FIG. 10B. In the related art, however, thereis a limit in processing. This is to say that the diameter of theindividual probe tip has served as a restriction so that a probe havinga probe-tip pitch of several μm could not be manufactured.

Conventionally, four-tip probes whose inter-tip distance is in the orderof millimeters to centimeters have been used, and many studies on thistype of probe were carried out. However, these conventional probescannot be applied to surface analysis of semiconductor devices.Recently, an undergraduate research group of Tokyo University released areport (Applied Physics, 70th Volume, 10th Issue, 2001) on measurementof electrical resistance of a silicon crystal surfaces using amicroscopic four-tip probe of a several μm pitch manufactured utilizingsilicon micro-processing technology, such as ordinary lithography. Foranalyzing the outermost or uppermost device-surface, however, thisseveral μm inter-tip distance is inadequate to achieve properperformance. An inter-tip distance of at most 1 μm or less is needed fordoing so. Even if the above-mentioned silicon micro-processingtechnology is employed, it is difficult to manufacture a four-tip probehaving an inter-tip distance of a such a sub-micron order.

In a further related art study, positioning of measuring points on anobject surface is carried out using an optical microscope. However,because a required measuring region for analyzing the outermost oruppermost device-surface is extremely small, it is difficult to achievepositioning using the conventional optical microscope and, as analternative means, a new observation technique, such as a scanningelectron microscope (SEM) and an atomic force microscope (AFM) has beenrequired. When an SEM is used, a sample is always irradiated withelectrons during observation. This may produce noise and render accuratemeasurement of electricity impossible. On the other hand, in the case ofan AFM, observation can be realized either in an ordinary atmosphericenvironment or a special atmospheric environment. However, when amulti-tip probe itself is used also as an image-obtaining probe, thismay be a hindrance to accurate measurement for reasons such as (1) it isdifficult to perform image analysis from signals detected by a pluralityof probe tips arranged in a row and (2) the image is contaminated orotherwise damaged by scanning. Further, in the conventional AFM, it is acommon practice to employ the light leverage method in which a mirror ismounted on a cantilever to detect displacement. In this case, a sampleis irradiated with laser light. Because laser light serves as anexcitation energy source to cause surface atoms to enter an excitedstate, this has a considerable effect on the movement of electrons on adevice surface and therefore also impedes accurate measurement ofelectricity. Alternatively, waves serving as excitation light can beremoved by wavelength cutoff using a filter. However, this alternativecannot realize observation in a perfect dark field and would oftenencounter problems, such as decreases in sensitivity due to attenuationof light intensity.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide aprocessing method to form a microscopic multi-tip probe whose inter-tipdistance is on a sub-micron order, and to thereby provide such amicroscopic multi-tip probe. Another object of the present invention isto provide an ultra-surface analyzing apparatus for analyzing theultra-surface of a semiconductor device, the apparatus having a functionof positioning that does not influence electricity measurement in anextremely small region using the microscopic multi-tip probe.

The multi-tip probe manufacturing method of the present inventioncomprises the steps of making a cantilever using lithographic techniquesand forming microscopic electrodes at a distal end of the cantilever bysputtering and gas-assisted etching processing using a focused chargeparticle beam.

This method of manufacturing a multi-tip probe of the present inventioncomprises the steps of, after making a cantilever using lithographictechniques, performing separation so as to form a plurality of leadportions using lithographic techniques on the cantilever and forming ashunt area at the distal end, and processing the shunt area of thedistal end using a focused charged particle beam using sputtering orgas-assisted etching, exposure to X-rays using a stopper, mask aligner,and Synchrotron Orbital Radiation (SOR), or by electron beam renderingand etching so as to form microscopic electrodes.

Further, the method of manufacturing a multi-tip probe of the presentinvention comprises the steps of, after making a cantilever usinglithographic techniques, performing separation so as to form a pluralityof lead portions using lithographic techniques on the cantilever, andblasting the distal end of the cantilever with a source gas andirradiating with a focused charged particle beam so as to formmicroscopic electrodes.

In order to provide the surface characteristic analysis device of thepresent invention with functions where the microscopic multi-tip probesare put into a non-contact state and an observed image is obtained for asample surface using an AFM function, a measurement region is specifiedfrom the observed image, and the multi-tip probes are positioned at thespecified regions and contact, is made, drive means are provided forpositioning probe positions of a cantilever having a microscopic,multi-tip probe of a pitch of 1 μm or less at a distal end and acantilever for AFM use having a dedicated probe at a distal end with aknown prescribed gap there between and driving the probes independentlyso as to, be in contact/non-contact states with respect to the samplesurface.

One of a bi-metal actuator, a comb-shaped electrostatic actuator, or apiezoelectric microactuator is adopted as the means for driving in acontact/non-contact state.

A self-detecting method where a strain gauge is installed on thecantilever is adopted to enable measurement in a dark field state.

A multi-tip probe of the present invention comprises a cantilever formedusing lithographic techniques, a plurality of lead portions formed onthe cantilever, and a plurality of electrodes connected to each of thelead portions so that the pitch between the electrodes is narrower thanpitch between the lead portions.

The multi-tip probe of the present invention may have a configurationprovided with a convex bank at the region where the electrode of thecantilever are formed or may be provided with probes at the electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an embodiment according to the presentinvention in which an elongated cantilever according to the presentinvention and its base portion are fabricated;

FIG. 2A is an enlarged view of a distal end portion of the cantileverfabricated by lithography, and FIG. 2B is a view showing a microscopicprobe tip formed by the etching process utilizing an FIB apparatus;

FIG. 3 is a view showing another embodiment in which an elongatedcantilever according to the present invention and its base portion arefabricated;

FIG. 4A is an enlarged view of a distal end portion of the cantileverfabricated by lithography, and FIG. 4B is a view showing a microscopicprobe tip formed by the CVD process according to an FIB apparatus;

FIGS. 5A-5D are views showing still another embodiment in whichvertically directed needle-shaped probe tips are formed on a comb-shapedelectrode by the CVD process according to an FIB apparatus;

FIGS. 6A and 6B are views showing a microscopic probe tip formed in aresilient shape by the CVD process according to an FIB apparatus; FIG. Ashows a bow type, FIG. B shows a coil type;

FIGS. 7A-7G are views showing a further embodiment in which asaddle-back-shaped convex bank is formed on a distal end portion of acantilever to stabilize the contact with a sample.

FIG. 8 is a view showing another embodiment in which a cantilever havingon its distal end portion four analysis-dedicated microscopic probe tipsand an AFM cantilever having on its distal end portion an AFM probe tipare juxtaposed in a manner that the respective probe tips are close toeach other.

FIG. 9A is a view showing a relation of contact in which the fouranalysis-dedicated microscopic probe tips and the AFM probe tip are incontact with a sample, FIG. 9B is a view showing the AFM probe tip movedto a raised position, FIG. 9C is a view showing the four microscopicprobe tips in contact with the sample, and FIG. 9D is an enlarged viewof the distal end portions of the two cantilevers;

FIGS. 10A-10B are views showing correlation between the inter-probe tipdistance and the depth of detection to a sample; and

FIG. 11 is a view showing a basic construction of an FIB apparatus usedin the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In a scanning tunnel microscope according to the four-tip probe methodto be used for semiconductor process evaluation, there is thecorrelation shown in FIGS. 10A and 10B between the inter-tip distanceand the depth of probing into a sample, as described above. Moreover, inorder to obtain information of an ultra surface, it is essential toarrange the probe tips at the corresponding narrow distances, as shownin FIG. 10B of the figure. In the related art, there is a limit inprocessing, and as the diameter of the individual probe tip isrestricted, an 8 μm pitch electrode is reported. However, a probe havingan inter-tip distance on the order of sub-microns cannot bemanufactured. Consequently, the present invention is intended firstly tofabricate a cantilever by the related method and then to form a probehaving a microscopic inter-tip distance by processing a distal endportion of the cantilever utilizing nano-processing technology.

For example, according to one technique, a single micro cantilever isfabricated by coating a substrate of silicon with a conductive thin filmor by implanting ions into a substrate to make the substrate conductive.The resulting micro cantilever has a multi-tip conductive portion whosetips are spaced one from another and a shunt area formed on a distal endportion of the cantilever into which area the tips of the conductiveportion merge. In order to obtain a less than 1 μm tip pitch,comb-shaped electrodes that are separated from each other are formed inthe shunt area of the distal end portion of the cantilever by an etchingprocess, such as sputter etching or gas assist etching using, forexample, a focused ion beam (FIB) apparatus. The comb-shaped electrodesare used as a multi-tip probe. According to another technique, a singlecantilever having a multi-tip conductive portion whose tips are spacedone from another and a non-conductive area formed at a distal endportion of the cantilever is fabricated using photolithographicprocesses. Further, the above-described structure is obtained bydepositing metal or carbon on the distal end portion of the cantilever,which is wired by a patch process, at desired distances by chemicalvapor deposition (CVD) using an FIB apparatus. The microscopic multi-tipconductive portions may be formed by making the silicon, i.e. thecantilever, conductive using ion implantation techniques throughirradiation with a beam rather than by CVD. It is possible to makeprocessing time shorter by making lead portions that are not required inthe microscopic processing as conductors for use with the multi-tipprobe, etc. in advance.

In another alternative, a needle-shaped electrode may be manufacturedwhich is comprised of not only the comb-shaped electrode, but also bylaminating or depositing a conductive substance (such as carbon ortungsten) on the distal end portion of the electrode. This electrode canmake contact with a sample in an improved manner. In the manufacture ofthe electrode by processing the deposited metal using an FIB apparatus,an ultra-microscopic multi-tip probe whose inter-tip distance is severalhundreds to several nm can be formed with ease, depending on the metalfilm thickness. In the foregoing description, an FIB is used as a sourceof a charged particle beam. Alternatively, however, the processing,which is gas assist etching or CVD, may be realized using an apparatususing an electron beam.

Further, for analyzing the outermost or uppermost surface of a device,it is essential to specify the position of the device surface.Conventionally, the positioning is carried out by obtaining an observedimage of the device surface of a sample on an optical microscope.However, because a measuring region is extremely small, specifying thedevice surface position using an optical microscope is difficult toachieve, requiring, as an alternative means, a new observationtechnique, such as a high-resolution scanning electron microscope (SEM)or an atomic force microscope (AFM). When an SEM is used, electrons areirradiated to a sample always during observation as mentioned above.This would be a cause for noise so that accurate measurement ofelectricity cannot be performed. For this reason, this type of surfaceobservation apparatus is inconvenient to use. When an observed image isobtained by an AFM, a laser to be used for measurement of displacementand serving as an excitation energy source would cause surface atoms totake on an excited state. In the present invention, as a solution tothis problem, an AFM not using a laser, namely, a method of detectingdisplacement of a device surface using a cantilever with a strain gaugeadhered thereto. As a solution to the above-mentioned problem thatimpedes accurate measurement for reasons, such as (1) it is difficult toperform image analysis from signals detected by a plurality of probetips arranged in a row and (2) the image is contaminated or otherwisedamaged by scanning, the present invention provides a single-tip probededicated to surface observation, in addition to a multi-tip probededicated to surface analysis, and also provides such a mechanism that,during scanning with the surface-observation-dedicated single-tip probeto obtain an observed image, a multi-tip probe serving as thesurface-analysis dedicated probe assumes a non-contact state to preventadhesion of contaminant or other damage, and it is possible for bothprobes to independently adopt contact or non-contact, positions. As thismechanism, a cantilever may be moved upwards and downwards by atemperature-controlled bimetal-type actuator, a comb-shapedelectrostatic actuator, or a piezoelectric micro-actuator.

First Embodiment

One embodiment will now be described in which a four-tip probe ismanufactured by a technique according to the present invention. Using asilicon substrate as a starting material, an elongated cantilever 1 of a16 μm width, which is shown in FIG. 1, and its base portion 2 arefabricated by lithography. Four lead paths 3 serving as prospectiveprobe tips are patterned in platinum film at distances of 35 μm apart inthe base portion 2 and at distances of 3.4 μm apart in the cantilever 1.The material of the lead paths 3 may alternatively be a different metal,such as aluminum or tungsten. The distal end portion of the resultantcantilever 1 is shown in enlarged scale in FIG. 2A. As is understoodfrom FIG. 2 a, the distal end portion of the cantilever 1 is taperedand, the individual lead paths 3 formed thereon by patterning extend toand terminate in a shunt area 4 serving as a common conductive portion.Using an FIB apparatus, the resulting distal end portion ismicroscopically processed to achieve the shaping and processing of fourprobe tips spaced at sub-micron distances. This sputter etching mayinclude removing only the platinum film or may include removing theplatinum film together with silicon substrate portions in a comb-shapedpattern to facilitate contact with a sample surface.

The basic construction of an FIB apparatus to be used in the presentembodiment is shown in FIG. 11. The FIB apparatus focuses ions, whichare derived from an ion source 71, into a focused ion beam by an ionoptical system 73 and irradiates a sample surface 79 with the focusedion beam 72. As the position to be irradiated is controlled by adeflector 77, electrons or secondary ions are emitted from theirradiated sample surface 79 and then detected by a secondary chargedparticle detector 78. The detected secondary charged particles aredependent on the sample surface material of an FIM-irradiated beam spot.Therefore, when the irradiated position is scanned two dimensionally, amicroscopic image of the sample surface can be obtained by combining theposition information and the detection information by a computer 76 anddisplaying the result of this combining on a display 75. This is thefunction of a scanning microscope according to an FIB apparatus. Theprocess in which the material of a sample surface is etched byirradiating the sample surface with the FIB is a sputter etchingfunction, and the process in which the material of a sample surface isetched as a chemical, reaction is facilitated by irradiating the FIB tothe sample surface while spraying an assist gas from a gas gun 74 is agas assist etching function. Further, the process in which a material isdeposited on a sample surface by irradiating with the FIB while sprayinga raw material gas from a gas gun is a Chemical Vapor Deposition (CVD)function.

In the present invention, using an FIB apparatus equipped with thesefunctions, a microscopic image of the distal end portion of theabove-mentioned cantilever 1 is obtained. As a result, the microscopicimage shown in FIG. 2A is obtained. Namely, position information aboutthe distal end portion of the cantilever 1 and pattern information aboutthe shunt area 4 of the distal end portion are obtained. In the presentembodiment, on the basis of this position information, the distal endportion is shaped into a rectangular projection 5 of 3.6 μm in width and2.5 μm in length, as shown in FIG. 2B, using the sputter etchingfunction of the FIB apparatus. Further, using the same sputter etchingfunction of the FIB apparatus, the rectangular projection 5 processed,and the conductive portion of the shunt area 4 is etched in such amanner that electrodes 6 spaced one from another by 0.8 μm distance areleft un-etched. As a result, a microscopic electrodes 6 and lead paths31, one connecting each microscopic electrode 6 and the respective leadpath 3, ar formed. By carrying out the sputter etching process of theFIB apparatus, the four-tip probe shown in FIG. 2B is formed on thedistal end portion of the cantilever. Alternatively, the same shapingmay be achieved by the gas assist etching process of the FIB apparatusinstead of the sputter etching process of the FIB apparatus. In thisalternative, the assist gas comprises a halogen, such as chlorine.

It is possible for the pattern-forming process of the shunt area 4 to becarried out using exposure to X-rays using a stopper, mask aligner, andSOR, or by electron beam rendering and etching.

Second Embodiment

Another embodiment will now be described in which a four-tip probe ismanufactured by another deposition technique of the present inventionusing an FIB apparatus. Using a silicon substrate as a startingmaterial, an elongated cantilever 1 of a 16 μm width, which is shown inFIG. 3, and its base portion 2 are fabricated by lithography. Four leadpaths 3, serving as prospective probe tips, are patterned at a spacingof 35 μm in the base portion 2 and at a spacing of 3.4 μm at thecantilever 1. The distal end portion of the resultant cantilever 1 isshown in enlarged scale in FIG. 4A. As is understood from FIG. 4A, thedistal end portion of the cantilever 1 is tapered and the individuallead paths 3 formed by patterning extend to and terminate in the distalend portion. The present embodiment is similar to the previousembodiment except that no conductive shunt area is formed. Using an FIBapparatus, the resulting distal end portion is microscopically processedto achieve the shaping and processing of four probe tips spaced atsub-micron distances.

In the present embodiment, using an FIB apparatus, a microscopic imageof the distal end portion of the above-mentioned cantilever 1 isobtained. As a result, the microscopic image shown in FIG. 4A isobtained. Namely, position information about the distal end portion ofthe cantilever 1 and position information about the terminal portion ofthe lead paths 3 at the distal end portion are obtained. In the presentembodiment, on the basis of this position information, conductiveportions are deposited on the distal end portion of the cantilever 1 asshown in FIG. 4B, using the CVD function of an FIB apparatus, as to formelectrodes 6 spaced from one another by a distance of 0.8 μm and leadpaths 31 connecting the microscopic electrodes 6 and a terminal portionof the respective lead path 3. Using phenanthrene as raw material gasfilled in a gas gun, the microscopic electrodes 6 and the lead paths 31are formed in carbon film on a silicon substrate. Further, the shapingby deposition is carried out in such a manner that the end portions ofthe microscopic electrodes 6 are extended. Thus, a four-tip probe shownin FIG. 4B is formed on the distal end portion of the cantilever 1 bythe CVD process of an FIB apparatus.

Third Embodiment

Another embodiment, unlike the previously mentioned embodiment usingonly a comb-shaped electrode, will now be described in which, in orderto improve the ease of contact with a sample, a needle-shaped electrodeis formed by laminating and depositing a conductive substance (such ascarbon or tungsten) on the distal end portion of each electrode by theCVD process using an FIB apparatus. FIGS. 5A-5D show the processingprocedures of the present embodiment, where FIG. 5A shows a state beforethe processing, and FIGS. 5B, 5C and 5D respectively show the statesafter FIB processes 1, 2 and 3. As shown, the processing procedures ofthe present embodiment are substantially similar to those of thepreviously mentioned embodiment with the exception of FIB process 3.Namely, what is shown in FIG. 5A is an elongated cantilever 1 fabricatedby lithography and having four-needle lead paths 3 patterned in platinumfilm. In FIB process 1, the distal end portion of the cantilever 1 isscaled by sputter etching using an FIB apparatus, thereby forming arectangular projection 5. Notably, this process is not absolutelyessential and may be omitted. Namely, the processing procedure mayadvance to the CVD process as with Embodiment 2, skipping FIB process 1.In FIB process 2, lead paths 31 connecting each microscopic electrode 6and the respective lead path 3 are microscopically formed on the distalend portion by the CVD process using an FIB apparatus, thereby shapingmicroscopic electrodes 6 spaced one from another by a sub-microndistance. Then, in FIB process 3, a vertically directed needle 61 isformed on each microscopic electrode 6 of the distal end portion furtherby the CVD process using an FIB apparatus. Because the thus formedneedle 61 contacts a sample surface, the present embodiment can improvethe ease of contact with a sample surface as compared to Embodiment 2using only the comb-shaped electrode. The forming of the verticallydirected needle 61 on each microscopic electrode 6 by the CVD processusing an FIB apparatus an be applied to the forming of microscopic probetips 6 in a spaced manner by etching a shunt area 4.

However, the needles 61 of the thus formed four microscopic electrodes 6would tend to cause erroneous conduction as they cannot uniformlycontact a sample due to their various heights, and would tend to causedifferent contact resistances due to various contact pressures. To avoidthese problems, in the present embodiment, a resilient probe 62 isformed in a bow; shape shown as electrode in FIG. 6A, thereby havingsuch a resilient structure that uniform contact pressure can be exertedon every probe tip. Alternatively, the shape of the resilient probe 62may be achieved by a coil shape shown in FIG. 6B. As a result, somevariation in height is allowed, so that the ease of manufacture of probetips can be increased drastically.

Embodiment 4

A still further embodiment will now be described in which, when anelongated cantilever 1 is fabricated by lithography, a protrusion in theform of a convex bank 11 is formed on the distal end portion of thecantilever 1 and four-probe-tip lead paths 3 are patterned in platinumfilm on the resulting cantilever 1, thereby causing uniform contactpressure to be exerted on every probe tip. FIGS. 7A-7G show thisprocessing procedure. What is shown prior to processing is thecantilever 1 fabricated by lithography. A cross-sectional view takenalong A-A′ that is a plan view of FIG. 7A is shown in FIG. 7D and 7E,the protrusion or bank 11 being the distal end portion of the cantilever1 is partially scaled by sputter etching using an FIB apparatus, therebyforming a rectangular projection 5. As is noted from FIG. 7E, in theresulting cantilever 1, a saddle-back-shaped convex bank 11 is leftun-scaled on the rectangular projection 5. In FIB process 2 shown inFIG. 7F and FIG. 7G, lead paths 31 connecting each microscopic electrode6 and the respective lead path 3 are microscopically formed on thedistal end portion by the CVD process using an FIB apparatus, therebyforming four probe tips spaced one after another by a sub-microndistance. As is apparent from FIG. 7G, the microscopic electrodes 6 aredeposited on the surface of the saddle-back-shaped convex bank 11 andhence have a saddle-back shape. Therefore, when the resulting cantilever1 is brought close to a sample surface, the crest of the saddle-backcomes into contact with the sample surface. In the case of the presentembodiment, if the crest of the protrusion or bank 11 at the distal endportion of the cantilever 1 is uniformly formed as the originalcantilever 1 is fabricated by lithography, the convex portion of themicroscopic electrodes 6 also are uniform in height, thereby causing astabilized contact relation between the sample surface and the pluralmicroscopic electrodes 6. Alternatively, the bank 11 at the distal endportion of the cantilever 1 may be formed by reactive dry etching or wetetching. Further, the forming of such a bank 11 on the distal endportion of the cantilever 1 can be applied to the forming of thecantilever having on its distal end portion a shunt area 4.

Embodiment 5

An embodiment of a surface characteristic analysis apparatus accordingto the present invention will now be described in which the apparatus isequipped with a probe of an atomic force microscope (AFM) so as to havea function of positioning the measuring point on an object surface. Asshown in FIG. 8, a cantilever 1 having on its distal end portion amulti-tip probe having four microscopic analyzing probe tips 6 and anAFM cantilever having on its distal end portion a single-tip probehaving an AFM probe tip 9 are juxtaposed in such a manner that the probetips 6 are close to the probe tip 9. The distal end portions of the twojuxtaposed cantilevers are shown, on an enlarged scale, in FIG. 9D. Asis noted from FIG. B, in the present invention, a pair of pads 10, 10′are formed one on each side of the base portion of the AFM cantilever 8,and a strain gauge 12 is built in the body of the ATM cantilever 8. Whenthe pads 10, 10′ are heated, the AFM cantilever 8 is retracted upward bya bimetal effect. In a state in which the pads 10, 10′ are not heated,the distal end portion of the AFM probe tip 9 comes into contact with asample surface and, at that time, the distal end portions of the fourmicroscopic probe tips 6 are moved away from the sample surface. To keepthis posture, it is essential to select the height of the AFM probe tip9 to meet the undulation of a sample. Generally, 5 μm to 20 μm isappropriate for the height. When the pads 10, 10′ are heated to retractthe cantilever 8 upward by bimetal effect, the distal end portion of theAFM probe tip 9 is retracted to a position above the distal end portionsof the four microscopic probe tips 6 as shown in FIG. 9B. At that time,the distal end portions of both the probe tips 6, 9 assume a non-contactstate with respect to a sample surface. Then, by moving a sample stage(not shown) in the Z (upward) direction, an adjustment is made in such amanner that the four microscopic probe tips 6 comes into contact withthe sample at an appropriate pressure, as shown in FIG. 9C. The contactpressure at that time is detected by a strain gauge mounted on thecantilever 1. The amount of displacement to retract must be the heightof the probe tip 9+α. Generally α is over 1 μm. This is true because,when the four microscopic probe tips 6 are brought into contact with asample surface at a predetermined pressure, possible deformation of thecantilever 1 is considered. If the AFM-cantilever detection method is ofa self-detection type in which a strain gauge is built in the cantileverbody instead of the light leverage method using laser light, possibleerrors due to excitation in this detection and the retraction of thedistal end portion can be avoided by observation and measurement in adark field state. Further, as a secondary effect, according to theconventional light leverage method, in the case of, for example, amulti-cantilever structure like the present embodiment, laser positiondetection systems equal or near in number to the plural cantilevers arerequired, which would be very complex in apparatus construction and verymeticulous and laborious in use, such as laser positioning. On thecontrary, according to the self-detection method, the apparatus can beconstructed with maximum ease, only requiring a plurality of electricalsignal outputs.

The operation of the apparatus according to the present embodiment willnow be described. Firstly, the cantilevers assume a non-heated state,namely, the distal end portion of the AEM probe tip 9 is positioned incontact with a sample surface and the distal end portions of the fourmicroscopic probe tips 6 are positioned away from the sample surface. Inthis state, the sample surface is scanned two-dimensionally to obtain athree-dimensional image of the sample surface. This operation is similarto that of the ordinary scanning probe microscope. The region of thesample to be measured is selected and specified from the obtainedthree-dimensional image in such a manner that the distal end portions ofthe four probe tips 6 come to a designated position. Because the distalend portions of the four microscopic probe tips 6 are spaced apredetermined distance from the distal end portion of the AFM probe tip9, such drift has to be corrected on the coordinate axis. The samplestage is driven in X and Y directions in such a manner that the distalend portion of the AFM probe tip 9 comes to a position deviated from thespecified measured position by the amount of the drift. As a result, thedistal end portions of the four probe tips 6 come to the designatedposition. Subsequently, the pads 10, 10′ are heated as shown in FIG. 9Bto cause the cantilever 8 to retract upward and, then, the sample stageis moved in the Z (upward) direction to make an adjustment such that thefour microscopic probe tips 6 come into contact with the sample at anappropriate pressure. The contact pressure at that time is monitored bythe strain gauge mounted on the cantilever 1. When it is recognized thata constant pressure is exerted on the sample, the four-probe-tipmeasurement is started to obtain data at that position.

Advantageous Results

The micro cantilever manufacturing method according to one aspect of thepresent invention comprises the steps of fabricating a cantilever havinga plurality of lead portions spaced one from another and a shunt areaformed at a distal end portion of the cantilever by a micro cantileverfabrication technique utilizing lithography, and forming a probe on thecantilever by processing the shunt area of the distal end portion of thecantilever by sputtering or gas assist etching using a beam of focusingcharged particles. According to another aspect of the present invention,the method comprises the steps of fabricating a cantilever having aplurality of lead portions spaced one from another, by a microcantilever fabrication technique utilizing lithography, and forming aprobe on the cantilever by CVD which irradiates a beam of focusedcharged particles to the distal end portion of the cantilever whilespraying a gas of raw material thereto. Therefore, it is possible toeasily obtain electrical information of microscopic portions andultra-surface, which was impossible in the conventional art. In themethod of manufacturing a microscopic multi-probe according to thepresent invention, because the probe tips are formed into a resilientstructure by CVD, some variation in height of the probe tips is allowed,thereby increasing the easiness of the probe tip fabricationdrastically.

The surface characteristic analyzing apparatus according to one aspectof the present invention comprises a micro cantilever having on itsdistal end portion a microscopic multi-tip probe, an AFM-dedicated microcantilever having on its distal end portion a dedicated microscopicprobe, the AEM-dedicated micro cantilever being spaced by a known,predetermined distance from the other micro cantilever, and means fordriving the two micro cantilevers independently of each other intocontact/non-contact states with respect to a sample. Therefore, theapparatus has the functions of obtaining an observed image of a samplesurface by an AFM with the microscopic multi-tip probe in a non-contactstate, determining a measuring region from the observed image,positioning the microscopic multi-tip probe in the determined measuringregion and bringing the microscopic multi-tip probe into contact withthe determined measuring region. Even in electricity measurement at anarbitrary position (e.g., a wiring portion) where positioning wasdifficult to take place on a conventional optical microscope, accuratemeasurement of electricity can be achieved by an array probe that can becombined with an AFM. Further, the means for driving the cantileversbetween a contact state and a non-contact state can be achieved withease by employing a temperature-controlled bimetal-type actuator, acomb-shaped electrostatic actuator, or a piezoelectric micro-actuator.Furthermore, by using the self-detection method in which a strain gaugeis mounted on the cantilever, electricity measurement in perfect darkfield can be realized.

1. A surface characteristic analysis apparatus comprising: a cantileverfor analysis having a multi-tip probe at a distal end thereof; an AFM(atomic force microscope) cantilever for AFM uses having an AFM probe ata distal end thereof and being positioned with a known prescribed gapbetween the two cantilevers; and driving means for driving the twocantilevers independently so as to be in contact/non-contact states withrespect to a sample surface, wherein the AFM cantilever measures a shapeof the sample surface while the multi-tip probe of the cantilever foranalysis is in a non-contact state with respect to the sample surface toselect a measurement region of the sample surface based on the measuredshape, and the cantilever for analysis analyzes the sample surfacewithin the measurement region with the multi-tip probe in a contactstate with the sample surface.
 2. A surface characteristic analysisapparatus according to claim 1, wherein the AFM cantilever is aself-detecting-type cantilever equipped with a strain gauge.
 3. Asurface characteristic analysis apparatus comprising: a first cantileverhaving a multi-tip probe at a distal end thereof; and a secondcantilever having a single-tip probe at a distal end thereof; whereinthe first and second cantilevers are mounted on a common base and drivenindependently of one another during use of the apparatus so that thesingle-tip probe can be positioned in contact with a sample surfacewhile the multi-tip probe is not in contact with the sample surface, andthe multi-tip probe can be positioned in contact with the sample surfacewhile the single-tip probe is not in contact with the sample surface. 4.A surface characteristic analysis apparatus according to claim 3;wherein the distal end portions of the first and second cantilevers aredisposed in juxtaposed spaced-apart relation.
 5. A surfacecharacteristic analysis apparatus according to claim 3; wherein themulti-tip probe has multiple tips that are spaced apart from one anotherin a widthwise direction of the first cantilever, and the single-tipprobe has a single tip that is spaced apart from the multiple tips inthe widthwise direction.
 6. A surface characteristic analysis apparatusaccording to claim 5; wherein the second cantilever is an AFM (atomicforce microscope) cantilever having an AFM single-tip probe.
 7. Asurface characteristic analysis apparatus according to claim 3; whereinthe second cantilever is an AFM (atomic force microscope) cantileverhaving an AFM single-tip probe.
 8. A method for analyzing a surface of asample using a first cantilever having a multi-tip probe and a secondcantilever having a single-tip probe, comprising the steps: observing animage of a sample surface using the single-tip probe of the secondcantilever while the multi-tip probe of the first cantilever is not incontact with the sample surface to select a measurement region of thesample surface; and analyzing the measurement region of the samplesurface using the multi-tip probe of the first cantilever while thesingle-tip probe of the second cantilever is not in contact with thesample surface.
 9. A method according to claim 8; wherein the observingstep is carried out with the single-tip probe in contact with the samplesurface.
 10. A method according to claim 9; wherein the observing stepis carried out by scanning the sample surface with the single-tip probe.11. A method according to claim 10; wherein the analyzing step iscarried out with the multi-tip probe in contact with the sample surface.12. A method according to claim 9; wherein the analyzing step is carriedout with the multi-tip probe in contact with the sample surface.
 13. Amethod according to claim 8; wherein the analyzing step is carried outwith the multi-tip probe in contact with the sample surface.
 14. Asurface characteristic analysis apparatus according to claim 8; whereinthe second cantilever is an AFM (atomic force microscope) cantileverhaving an AFM single-tip probe.